Internal combustion engines (and particularly boosted or turbo charged engines) have a tendency to collect unwanted carbon deposits on the back side or fillet region of the intake valve as well as the choke area within the cylinder head immediately surrounding the intake valve. Such carbon deposits, commonly referred to as soot, result from the normal combustion process and can become attached to the metal surfaces of the valve and cylinder head by heat and pressure. As additional layers of soot begin to build up on top of one another, they may cause a restriction in the air intake path and therefore reduce the mass airflow to the cylinders. This may result in a decrease in overall efficiency of the engine. Even a single layer of soot may cause the surface texture of the collection area to be somewhat rough which may tend to increase the rate or likelihood of soot particle adhesion.
Cam phasing (late closing intake valve) may tend to exacerbate buildup of soot deposits immediately upstream from the intake valve because hot combustion gases are pushed back upstream from the combustion chamber into the air intake path, thereby heating that area. In addition to carbon from the combustion gasses, any engine crank case oil or other contaminants hanging in suspension or entrained in the inlet air charge collecting in this area will be turned to soot by the heat from the combustion gasses.
Possible sources of crank case oil present within the engine air path may be the positive crank case ventilation (PCV) system, exhaust gas recirculation (EGR) system, oil separation system, and/or leakage from turbo charger/super charger seals.
Internal combustion engines that use port fuel injection (PFI) technology have the fuel injectors located so as to inject fuel into the intake air before it passes through the intake valves into the cylinders. This allows the injector cone angle to be targeted so as to spray fuel at the back of the intake valve when in the open position, thereby delivering fuel directly onto the area where soot/carbon collection is known to be the most likely. The fuel spray has a cooling effect and, if a solvent or cleaning solution is included in the fuel formulation, may also have a self-cleaning effect.
In engines that utilize direct injection (DI) technology, however, the fuel is injected directly into the cylinder. Thus the fuel does not contact the back sides of the intake valves, so the cleaning/cooling effect present in the PFI system is not available.
It is known to clean undesirable deposits within a motor vehicle engine when the vehicle is in a maintenance garage, repair shop, or otherwise out of service. In general, this is performed by connecting a delivery tube to the air induction system of the engine while the vehicle is stationary and, after starting the engine injecting a cleaning solution. U.S. Pat. No. 4,989,561 teaches a cart-mounted pumping unit that is connected with an engine by attaching a solution-carrying tube when a tube is fitting into the engine. Other electrical connections are made with the engine by which the fuel injectors and ignition are monitored and/or controlled so that the cleaning solution is supplied in the correct amount and at the proper time.
Such systems require that the vehicle be taken out of service for some length of time, as at least some degree of disassembly of the engine and/or air induction system is necessary. The temporary connections with the induction system also raise issues of how to achieve an adequate seal between the solvent delivery tube and the induction system.